The Ocaml way would be to define the functions in separate modules (A.foo, B.foo, etc.). There are convenient syntaxes for declaring which modules are in scope

The Ocaml way would be to define the functions in separate modules (A.foo, B.foo, etc.). There are convenient syntaxes for declaring which modules are in scope in a given expression, as well as support for first-class modules (you can define functions that take modules as parameters). The module system is sophisticated, and is arguably the "power feature" of Ocaml.